The present disclosure relates to the subject matter contained in Japanese Patent Application No.2001-114148 filed Apr. 12, 2002, which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a vehicular electronic device in which a case that houses a circuit board and a connector, and brackets for attaching the case to a vehicle are formed integrally with each other.
2. Description of the Related Art
A vehicular electronic device according to the related art will be described with reference to the accompanying drawings.
FIGS. 1(a) and 1(b) are views showing a manner of attaching a vehicular electronic device to a frame of a vehicle. The direction of the arrow E indicates the longitudinal direction of the vehicle. In FIG. 1, (a) is a plan view, and (b) is a view looking in the direction of the arrow E. FIG. 6 is an exploded perspective view of a conventional vehicular electronic device. FIG. 7 is a section view of the conventional vehicular electronic device, taken along the line Bxe2x80x94B of FIG. 6. FIG. 8 is a view showing a state where the conventional vehicular electronic device is broken by an impact load.
The vehicular electronic device is configured by a case 91 made of an aluminum die casting, a printed circuit board 2, a lid 3, and a connector 4.
As shown in FIG. 1, the vehicular electronic device is attached to a frame 80 of the floor of a vehicle.
The case 91 is made of a light aluminum die casting which has a function of electromagnetically shielding the printed circuit board 2, and which prevents the main unit of the electronic apparatus from being damaged in a collision of the vehicle. A space for housing the printed circuit board 2 and the like is formed inside the case 91. A cutaway 121 through which the connector 4 is to be passed is formed in one of four side walls 12. Three brackets 15 for attaching the vehicular electronic device to the frame 80 of the vehicle are extended from the outer faces of the side walls 12 of the case 91. Each of the brackets 15 has an abutting face 17 which is to abut against the frame 80 of the vehicle, and an attachment hole 16 through which an attachment screw 85 is to be passed.
In the printed circuit board 2, the external shape has dimensions which allow the board to be housed in the space of the case 91, attachment holes 23 are formed respectively in the four corners at the same intervals as those of screw holes 14 of the case 91, and copper patterns are formed on both the faces. An acceleration sensor 21 and another electronic component 22 are mounted on the upper face (on the side of the top plate 5 of the case) of the printed circuit board 2.
The lid 3 is configured by a steel plate. In the lid, the external shape has dimensions which allow the lid to be housed in the space of the case 91, attachment holes 24 through which screws are to be passed are formed respectively in the four corners at the same intervals as those of the screw holes 14 of the case. A rib 31 which is slightly raised is formed on the whole periphery of the lid 3. The lid exerts functions of dustproof and electromagnetic shielding on electronic circuits, and prevents the copper patterns and the components from being damaged by an external force.
The connector 4 is an output terminal through which an ignition command generated by the acceleration sensor 21 or the other electronic component 22 is transmitted to a gas generator of an air bag.
Next, the assembly structure will be described with reference to the accompanying drawings.
FIG. 7 is a section view of the conventional vehicular electronic device, taken along the line Bxe2x80x94B of FIG. 6.
The printed circuit board 2 abuts against mounting faces 13 in a state where the face on which the acceleration sensor 21, the other electronic component 22, and the connector 4 are mounted is opposed to the top plate 5. The connector 4 is engaged with the cutaway 121 of the case. An end portion 31a of the rib 31 of the lid 3 abuts against the printed circuit board 2. The case 91, the printed circuit board 2, and the lid 3 are stacked in this sequence and then fastened together by four screws 86.
In the above-described vehicular electronic device, the side walls 12 of the case 91 have a uniform thickness, and the plural brackets 15 are formed integrally on the outer faces of the walls. When the frame 80 is deformed by a collision or the like, therefore, the side walls 12 are sometimes deformed in a region H (see FIG. 8) ranging from the root portion of the top plate 5 to the printed circuit board 2 as shown in FIG. 8. At this time, there is a possibility that the printed circuit board 2 or the components of the vehicular electronic device is damaged (Y of FIG. 8), or that broken pieces 91a of the aluminum die casting due to bending or breakage of the side walls 12 of the case 91 are scattered (X of FIG. 8) and fall on the electronic components or the patterns, thereby causing a short circuit.
The invention has been conducted in order to solve the above-discussed problem. It is an object of the invention to maintain functions of a vehicular electronic device even when an impact is applied to a vehicle and the frame 80 is subjected to deformation such as bending or compression. It may be the functions of the vehicle electronic device to be maintained that the acceleration sensor 21 detects the impact and the other electronic component 22 transmits an ignition command to an air bag.
In order to attain the object, according to a first aspect of the invention, there is provided a vehicular electronic device having a circuit board, a case, a connector, and a bracket. The circuit board performs a predetermined control in a vehicle. The case houses the circuit board. The connector electrically connects the circuit board with an outside. The bracket is formed integrally with the case and attaches the case to the vehicle. The case has a first portion and a second portion. The first portion is thicker than the second portion. The second portion continuously extends to the bracket.
According to a second aspect of the invention, the first portion defines space in which the circuit board is housed.
According to a third aspect of the invention, when the case is attached to the vehicle, the first portion is thicker than the second portion in a longitudinal direction of the vehicle.
According to a fourth aspect of the invention, the circuit board controls an air bag.